Railway signal control circuit



y 5, 1942- F. H. NICHOLSON 2,282,083

- RAILWAY SIGNAL CONTROL CIRCUIT Filed Nov. 50,.1940

" f I I Marie? Mamm l Feedflaelr INVENTOR Fiwgk H/Vebfialron m Q 4 c 425 HIS' ATTORNEY Patented May 5, 1942 1 f UNITED STATES PATENT OFFlCE RAILWAY SIGNAL CONTROL CIRCUIT of Pennsylvania Application November 30, 1940, Serial No. 357,973

12 Claims.

My invention relates to circuits for controlling railway signals and it has special reference to the utilization by such circuits of the coded feed back operating principle that first was disclosed by my patent No. 2,021,944 (issued November 26, 1935) and that also is shown by numerous later patents and applications of common ownership herewith.

Broadly stated, the object of my invention is to improve the organization of the apparatus which supplies the conductors of such circuits with pulses of feed back energy that recur in step with the off period intervals of the master control circuit code.

A more specific object is to facilitate the con trol of feed back energy applying relays of the impulse type which devices IR. of Herman G. Blosser Reissue Patent No. 21,783 (granted April 29, 1941) exemplify.

Another object is to simplify the structure and increase the power economy of the pick-up circuits for such impulse relays when those relays are used in systems wherein the master energy operated code following relay is supplemented by a code following repeater, such as is shown (at TR) in Fig. 3 of the Blosser reissue patent above named.

In practicing my invention I attain the above and other objects and advantages by: (1) eliminating all transformer devices from the impulse relay pick-up circuit; (2) carrying this circuit directly over a back contact of the master energy operated code following relay; and (3) serially including in this circuit a contact of a repeater relay which is closed when the code following relay is picked up and which opens after a slight delay upon each code following relay release.

I shall describe three forms of feed back energy supply apparatus embodying my invention and shall then point out the novel features thereof in claims. These illustrative embodiments are disclosed in the accompanying drawing in which:

Fig. 1 is a diagrammatic representation of a track type of control circuit equipped with the improved feed back supply apparatus of my invention and organized to form part of an automatic block signaling system having coded feed back approach lighting control;

Fig. 2 is a representation of master and "feed back codes for the control circuit of Fig. 1;

Fig. 3 is a partial reproduction of the feed back supply apparatus of Fig. 1 showing how the im pulse relay pick-up circuit thereof is modified upon change of the repeater relay from a back to a front contact controlled device; and

Fig. 4 shows feed back supply apparatus Wherein the master code following relay is rendered unresponsive tothe off period feed back pulses by means external to the impulse relay.

In the several views of the drawing like reference characters designate corresponding parts. Referring first to Fig. 1, the improved control cir cuitorganization of my invention is there disclosed in association with a coded track circuit system of automatic block signaling for a railway track I--2 over which it will be assumed that traffic moves in the single direction indicated by the arrow, or from left to right in the diagram. The protected stretch of this track is divided into the customary successive sections by insulated rail joints 3 and the rails of each section form part of a track type of control circuit which normally is capable of transmitting energy between its two ends but which at times is rendered incapable of such transmission.

In this view of Fig. 1 reference characters D and E respectively designate the entrance and the exit ends of one of these track sections which is illustratively shown as being a full signal block in length; character TR. designates a code following track relay which is installed at the entrance end of the section and operated by energy received from the rails thereof; character TB is a track battery or other master energy source provided at the section exit for the purpose of supplying these rails with the relay operating energy just referred to; character CTM a coding device having a contact 5 which codes this energy by periodically interrupting the rail supply circuit; and character S the usual wayside signal which guards the entrance of each of the track blocks and which is controlled by the associated track relay TR through the medium of a repeater relay TM and decoding apparatus DA.

,-An automatic block signaling system of the referred to coded track circuit. type operates without the aid of line wires and in the representative form that is disclosed by Fig. 3 of the earlier identified Blosser Reissue Patent No. 21,783 it includes all of the elements above named. Such a system further comprises the customary facilities (not shown in Fig. 1) for continuously operating each of the exit end relays CTM at one or another of the usual plurality of distinctive code rates. Selection among these rates (which in a typical three-indication system may consist of and energy pulses per minute) is made accordance w t advance. traf ic coin ditions by the decoding apparatus DA functioning in customary manner.

This decoding apparatus (details not shown in Fig. 1) is controlled in the usual fashion by the code following repeater. relay TM and it performs the further function of selectively setting up a lighting circuit for one or another of the signal lamps (G, Y and R in the typical threeindication system above referred to) of the wayside signal S at the same location.

Typically, such decoding apparatus requires that the code following relay which controls it make use of a plurality of contacts and in Fig. 1 two such contacts are indicated at 6 and 1. As might be expected, however; this multiplicity of contacts causes the decoding control relay to require an increased amount of operating energy.

When the track sections of the signaling systern are comparatively short, energy of this increased intensity can quite readily be transmitted (from the exit end source TB) to the relay directly over the. sectionrrails l -'2 and" contacts 6-! .may then be carriedv by therail-energi'zed track relay TR. In such short track circuit applications, accordingly, repeater. devices of the character shown at :TM obviously are notneeded.

Vihen, however; the length of the track circuit exceeds say a mile or a mile and a half, difficulty is experienced in operating'a multi-contact track relay by the comparatively weakenergy that is received from the rails and resort then must be had to the repeater relay'TM. As thedrawing shows, this repeater relay carries the decoding control contacts 6-! and it is energized locally under the controlof a single contact 8' of the track relay TR.

When provided witlr this single "contact ;only,

:relay TR picks up on a much smaller-intensity of trackway energy than does a multi-cont'act de vice. The reduction in energy requirements is, in fact, so great that code following trackrelays of the single contact type (device TR of Fig. 1) can be operated with complete dependability over track circuits having lengths of two miles or more.

The repeater relay TM which makes'this extended track circuit length possible may be picked up either over a back point of the track relay contact 3, as shown in Fig. 1, orover a front point of the track relay contact, as shown in Fig. 3. In both instances the decoding contacts 6-? of relay TM repeat allcode following operations of the controlling contact 8 of track relay TR. In the former, relay TM is released when relay TR is picked up and picked up when relay TB is released; in the latter, relay TM is picked up when relay TR is picked up and released when relay TR is released.

In order that the wayside signal Se may be kept dark as long assection DE-remains vacant and lighted only when a train places a' shunt-across the section rails th'e lamp energizing circuits therefor are carried over a back contact '9 of an approach relay AR at the section exit E. This relay is slow releasing and as long asthe winding thereof is recurrently energized at code speed rate, contact 9 occupies the picked up position wherein the signal circuits are disconnected from their lighting supply source.

Controlling this approach relay energization is a detector relayKR. Each time that a contact H thereof is picked up at a time when a contact l2 of the coding device CTM is released; relay AR is energized over a circuit that extends fromthe I positive terminal of a local supply'source, through back contact l2, the winding of relay AR, front contact H of relay KR, and a stick winding !3 of that relay back to the negative terminal of the supply source. For a more complete description of this circuit reference may be had to a copending application Serial N 0. 354,097 filed by Herman G. Blosser onAugust 24, 1940.

The main or pick-up winding E5 of the detector relay KR is connected with the section rails during and only during the frnaster code off" periods. This connection is established at the back. point of coding contact 5 and over it oh period pulses of feed back current (from the section entranceD) are supplied to' winding 15 as long as the section remains vacant. These pulses recurrently pick up the detector relay contact l l and thereby cause the approach relay AR to keep 'sig'nal' Se deenergized.

. These detector relay energizing pulses of feed back energy are supplied to the section rails by apparatusthat is installed at the entrance 'loca- .tion D4; This apparatus comprises? (1) a source "of feedback? energy AB; (2) "an impulse relay of the-named off code periods.

The just named impulse relay IR may be of the same type as the earlier mentioned Blosser ReissuePatent No. 21 ,783 shows and describes. As long as the winding thereof remains deenergized, contact I stays released and connects the operating winding of track relay TR directly across the sectionrails. Upcnenergization of the impulse relay winding-, -however;contact H- picks up and then transfers the connection ofthe section rails from the relay TR to the feed back energy source parent from later referencesto the code diagrams of Fig. 2.

The improvements of my invention reside in the'circuit over'which'this impulse relay IR is picked up during each ofi period of the received master code. This pick-up circuit may be energized from any suitable local source, such as the terminals plus and minus designate, and in the form shown in Fig. 1 it includes a back contact 8 of the code following relay TR connected in series with a back contact IQ of the repeater 1 relay TM.

"Under conditions (section DE vacant) of 1 master code energy reception at location D: (l) .1 the trackrelay TRholds contact 8 picked up I. during.- each on period of the received (from 0.53

exit endsource TB) master code and releases contact 8 during each ofi period interval of that code; and (2) the repeater relay TM keeps contact I9 released during each on period of the same received code and picks up contact I 9 early during each 01f period of that code.

' The pick-up circuit for impulse relay IR is, in

consequencakept deenergized (at contact 8) during each of those master code on periods and contact 11 of that relay then keeps relay TR connected with the section rails in the desired manner.

Upon each off period release of relay TR, however, contact 8 of that relay reaches its released position before contact I9 of relay TM leaves its released position and thus energizes the impulse relay over a path that extends from the positive supply terminal through back contact 8, conductor 2|, back contact l9, conductor 22 and the impulse relay winding back to the negative supply terminal.

This interval of pick-up circuit completion, while momentary, is sufiicient to cause relay IR to move contact IT to the picked up position in which the connection of the section rails is transferred from relay TR to the feed back energy source AB. Once so picked up, contact i! there continues for the full release period of relay IR and thereby prolongs the resulting pulse of feed back trackway energy considerably beyond the point in the off code period that repeater relay contact 9 picks up and breaks the impulse relay pick-up circuit.

As previously stated, the period of release delay for the impulse relay IR i chosen to be somewhat less than the oil period length of the fastest master code to which the track relay TR is called upon to respond. The reason for this choice will become evident upon inspection of Fig. 2.

As is there shown, each feed back energy pulse begins early in the master code off period during which it occurs. Were relay IR to be quick releasing, the feed back pulse would terminate upon interruption of the impulse relay pick-up circuit and thus be much shorter than is either necessary or desirable. By making relay IR slow releasing, the duration of the feed back pulse is prolonged to a point close to the off period end.

Never, however, may it extend beyond the end of the shortest master code 011" period, otherwise the track relay TR would still be disconnected from the section rails at the beginning of the succeeding on code period. Hence the release delay for relay IR always is kept within the limits previously stated.

Referring now to Fig. 3, I have there shown the entrance end apparatus of Fig. 1 modified to include a front contact repeater TMI for the code following track relay TR.

This repeater relay TMI is similar to device TM of Fig, l and diiTers therefrom only in that it receives pick-up current over the front point of track relay contact 8 and in that it is provided with a short period of release delay. Contacts 5, 1 and [9 thereof are icked up during each on period pulse of the received master code and are released during each oif period interval of that code.

The impulse relay pick-up circuit of Fig. 3 includes (like the circuit of Fig. 1) back contact 8 of relay TR connected in series with contact IQ of the repeater relay TMI. In this Fig. 3 organization, however, contact I!) effects circuit completion when picked up and circuit interruption when released.

The control of impulse relay IR which the pickup circuit of Fig. 3 exercises is the full equivalent of that explained for the organization of Fig. 1. Under conditions of master code reception relays TR and TMI are both picked up during each on period of the received master code and both released during each off period of that code.

The pick-up circuit for impulse relay IR is.

- type of rectifier 24.

in consequence, deenergized (at-contact 8) during each of those master code on periods and contact ll of that relay then keeps relay TR connected with the section rails in the desired manner. Upon each off period release of relay TR, however, contact 8 of that relay reaches its released position before contact 19 of relay TMl leaves its picked up position and thus completes the pick-up circuit for the impulse relay.

In this manner relay IR is caused to pick up contact I! early during each ofi period of the received master code. Even though contact I9 almost immediately releases (and interrupt the impulse relay pick-up circuit), contact l'l' continues pickup until the expiration of the impulse relay delay period and thus continues the connection of feed back source AB with the section rails until close to the end of the oil code period, as shown in Fig. 2.

-Upon that relay expiration, contact ll releases and by reconnecting the track relay TR with the section rails reconditions that relay for reception of and response to another on period pulse of master code energy.

In each of the just described Figs. 1 and 3 the impulse relay IR is arranged to disconnect the track relay TR from the section rails during each periodof feed back source connection therewith. While this is a very desirable method of insuring the track relay against false pick-up during the off period intervals of feed back energy supply it is by no means the only method available for accomplishing the named result.

One alternative method is illustrated in Fig. 4.

- There the track relay TR is continuously connected with the section rails |-2 through a static This rectifier is poled in opposition to the polarityof the energy which feed back source AB supplies to the rails when contact I! of the impulse relay IR is picked up and in consequence current from source AB is excluded from the track relay winding as effectively as were that Winding to be disconnected from the rails at the back point of contact H, as in Figs. 1 and 3.

Quite obviously the impulse relay IR of Fig. 4 may have exactly the same characteristics as in either of Figs. 1 and 3 and may be operated over the pick-up circuit which each of those two fiigures shows. The improved pick-up circuit of my invention, therefore, is not limited to impulse relays which disconnect the code following relay from the control circuit conductors during the ofi code periods but may be used with any impulse relay that connects a feed back source with those conductors when picked up and breaks that connection when released.

The improved impulse relay control facilities of my invention are, moreover, not restricted to control circuits of the track type herein disclosed but they also have utility when applied to coded feed back circuits of any other form wherein the conductors lose their normal energy transmitting capability under certain conditions only.

Thus, instead of being track rails as shown, the control circuit conductors I2 may also take the form of line wires which connect master energy supply and feed back energy receiving equipment (see device TB-CTMKR of Fig. l) at one end of the circuit with master energy receiving and feed back energy supply equipment (see devices TR-TM-AB-IR of Fig. l) at the other end of the circuit.

When used with a control circuit of the line conductor type 'J'ust described anaimpulsearelay equipped" with theximprovedpick-up circuit faciltions of the coded feed back? class.

ities; of my invention will function in exactly the same ,manneras when usedwith; the track time of control circuits that are herein disclosed. My invention is, therefore, one of broad ,utilitypand is not to be restricted to the specific forms or applications that I have shown byway of illustration.

From the foregoing "description of Figs. 1 to 4, therefore, it will be seen thatI have made im- Although I have herein shown and described i only three forms of railway trafilc controlling apparatus embodying my invention; it is understood that various changes and modifications may be made'therein within the'scope of the appended claims without departing from the spirit and scope of my invention.

Having thusdescribed my invention; what I claim is:

1. In a railway signaling system, the combination of a control circuit which comprises a pair of conductors, means for supplying said conductors with master code energy in the form ofrecurring on period pulses that are separated by off period intervals, a code following relay connected with said conductors and operated from a released to a picked up position by and only by each of the said on period pulses of master code energy that said connection transm-its, a repeater relay controlled by said code following relay and occupying a first position when the code following relay is picked up but shifting after a slight delay to a second position upon each release of the code following relay, a source of feed back energy, an impulse relay which in picking up connects said feed back energy source with said control circuitconductors and which in releasing interrupts that connection, an energizing circuit for said impulse relay which includes a back contact of said code following relay connected in series with a contact ofsaid repeater relay that is closed in said first position and over which each release of said code following relay contact momentarily picks up the impulse relay and thereby causes said circuit conductors to be supplied with a pulse of feed back energy during the ofi code period of said release, and traffic governing apparatus controlled by the pulses of said feed back energy which said circuit conductors transmit.

2. In a railway signaling system, the combination of a control circuit which comprises a pair of conductors, means for supplying said conductors with master code energy in the form of recurring on period pulses that are separated by off period intervals, a code following relay connected with said conductors and operated from a released to a picked up position by and 1 only by-each of the said on period pulses of master code energy that-said connection transniits, a repeater relay energized over a back conr tact of said code following relay-and occupying a released position when the code following relay is picked upbut. shifting after a slight delay to a picked up position upon each release, of the code following relay, a source of feed back energy, an impulse relay whichin picking up connects said feed back energy source with said control circuit conductors and which in releasing interrupts that connection, an energizing circuit for said impulse relay which includesiaback contact of said code following relay connected in series with a backcontact of said repeater relay and over which each release of said code following. relayrcontact momentarily .picks up theimpulse relay and thereby causes said circuit conductors to be supplied with a pulse cf feed. back energy=during the ofi code period of said re lease, and traffic governinglapparatus controlled by the pulses of said feed back energywhich said circuit conductor'stransmit.

3. In a railway signaling system, thecoinbination of a control circuit which comprises a pair of conductors, means for supplying. said conductors with master code energy in the form of recurring on period pulses that are separated by off periodintervals, a code following-relay connected with said conductors and operated from a released to atpicked up vposition by and only by each of thesaid for period pulses of master code energy that said connection transmits, a repeater relay energized over a front contact of said code following relay and 0ccupying a picked up position. when the code following relay is picked upbut shifting after a slight delay to a released position. upon each release of the code following relay, a source of feed back energy, an impulse relay which in picking up connects said feed back energy source with control circuit conductors and which in releasing interrupts that connection, anenergizing circuit for said impulse relay which includes a back contactoi said code following relay connected in series with a front contact of said repeater relay and over which each release of. said code following relay contact momentarily picks up the impulse relay and thereby-causes said circuit conductors to be supplied with a pulse of feed back energy during the off code period of said release, and traffic governing apapparatus controlled by the pulses of said feed back energy which said'circuit conductors transmit.

4. In a railway signalling system, the combination of a control circuit which comprises a pair of conductors, means for supplying. said conductors with master code energy in the form of recurring on period pulses that are separated by ed period intervals, a code following relay connected with said conductors and onerated from a released to a picked up position by each of the said on period pulses, of master code energy that said connection transmits,

repeater relay controlled by said code following relay and occupying a first position when the code following relay is picked up but shifting after a slight delay to a second position upon each release of the code following relay, a source of feed back energy, an impulse relay which in picking up transfers the connection of said control circuit. conductors from saidcode following relay to said feed back energy source and which in releasing restores the control circuit connection to the codefollowingrelay, an energizing circuit forvsaid impulserelay which includes a back contact of. said code following assacss relay connected in series with a contact of said repeater relay that is closed in said first position and over which each release of said code following relay contact momentarily picks up the impulse relay and thereby causes said circuit conductors to be supplied with a pulse of feed back energy during the off code period of said release, and traffic governing apparatus controlled by the pulses of said feed back energy which said circuit conductors transmit.

5. In a railway signaling system, the combination of a control circuit which comprises a pair of conductors, means for supplying said conductors with master code energy in the form of recurring on period pulses that are separated by off period intervals, a code following relay connected with said conductors and operated from a released to a picked up position by each of the said on period pulses of master code energy that said connection transmits, a repeater relay controlled by said code following relay and occupying a first position when the code following relay is picked up but shifting after a slight delay to a second position upon each release of the code following relay, a source of feed back energy, an impulse relay having a release delay which is appreciable but less than the off period length of said master code and provided with a contact which in picking up transfers the connection of said control circuit conductors from said code following relay to said feed back energy source and which in releasing restores the control circuit connection to the code following relay, a pick-up circuit for said impulse relay which includes a back contact of said code following relay connected in series with a contact of said repeater relay that is closed in said first position and over which each release of said code following relay contact momentarily energizes the impulse relay and thereby causes said circuit conductors to be supplied with a pulse of feed back energy during the ofi code period of said release, and traffic governing apparatus controlled by the pulses of said feed back energy which said circuit conductors transmit.

6. In a railway signaling system, the combination of a control circuit which comprises a pair of conductors, means for supplying said conductors with master code energy in the form of recurring on period pulses that are separated by off period intervals, a code following relay connected with said conductors and operated from a released to a picked up position by each of the said on period pulses of master code energy that said connection transmits, a repeater relay energized over a-' back contact of said code following relay and occupying a released position when the code following relay is picked up but shifting after a slight delay to a picked up position upon each release of the code following relay, a source of feed back energy, an impulse relay which in picking up transfers the connection of said control circuit conductors from said code following relay to said feed back energy source and which in releasing restores the control circuit connection to the code following relay, an energizing circuit for said impulse relay which includes a back contact of said code following relay connected in series with a back contact of said repeater relay and over which each release of said code following relay contact momentarily picks up the impulse relay and thereby causes said circuit conductors to be supplied with a pulse of feed back energy during the off code period of said release, and traffic governing apparatus controlled by the pulses of said feed back energy which said circuit conductors transmit.

7. In a railway signaling system, the combination of a control circuit which comprises a pair of conductors, means for supplying said conductors with master code energy in the form of recurring on period pulses that are separated by off period intervals, a code following relay connected with said conductors and operated from a released to a picked up position by each of the said on period pulses of master code energy that said connection transmits, a repeater relay energized over a back contact of said code following relay and occupying a released position when the core following relay is picked up but shifting after a slight delay to a picked up position upon each release of the code following relay, a source of feed back energy, an impulse relay having a release delay which is appreciable but less that the 01f period length of said master code and provided with a contact which in picking up transfers the con- .nection of said control circuit conductors from said code following relay to said feed back energy source and which in releasing restores the control circuit connection to the code following relay, a pick-up circuit for said impulse relay which includes a back contact of said code fol- Y thereby causes said circuit conductors to be supplied with a pulse of feed back energy during the off code period of said release, and trafhc governing apparatus controlled by the pulses of said feed back energy which said circuit conductors transmit.

8. In a railway signaling system, the combination of a control circuit which comprises a pair of conductors, means for supplying said conductors with master code energy in the form of recurring on period pulses that are separated by off period intervals, a code following relay connected with said conductors and operated from a released to a picked up position by each of the said on period pulses of master code energy that said connection transmits, a repeater relay energized over a front contact of said code following relay and occupying a picked up position when the code following relay is picked up but shifting after a slight delay to a released position upon each release of the code following relay, a source of feed back energy, an impulse relay which in picking up transfers the connection of said control circuit conductors from said code following relay to said feed back energy source and which in releasing restores the control circuit connection to the code following relay, an energizing circuit for said impulse relay which includes a back contact of saidcode following relay connected in series with a front contact of saidrepeater relay and over which each release of said code following relay contact momentarily picks up the impulse relay and thereby causes said circuit conductors to be supplied with a pulse of feed back energy during the off code period of said release, and trafiic governing apparatus controlled by the pulses of said feed back energy which said circuit conductors transmit.

9. In a railway signaling system, the combination of a control circuit which comprises a pair of conductors, means for supplyingsaid con-.- ductors withimaster code energy. in the form of recurring on? period pulses that are separated by off period intervals, a codefollowing relay connected. With-said conductors and operated from a releasedrto a picked .up position by eachof the said on period pulses of master code energy that said connection transmits, a repeater relay energized .over a front contact :of

up. position when the '7 code following relay .is picked up but shifting after a slight delay to .10 said code following relay and occupying a picked a released position upon each releasev of the code following relay, a source ofifeed back ens ergy, an impulse relay' having a release delay whichiis appreciablebut less than the off pe-' riod length of said master code and provided with a contact which in picking .up transfers the connectionof said control circuit conductors from said code following. relay to said feed back:

energyisource and which in releasing restores the control circuit connection to .the code following relay, a pick-up circuit for .saidimpulse. relay;

which includes a back contact. of saidcode following relayrconnected in .series with a front contact. of said repeater arelay'and over which each release of said code following relay contact momentarily energizes; the impulse relay and.

thereby causes said circuit conductors to be supplied with a pulse of feed back energy during the off code period of said release, and traffic governing apparatus controlled .by the pulses. of said feed back energy which said circuit conductors transmit:

10. In a railway sighaling'system, the Com: bination of a control circuit which comprises a pair of conductors, means for supplying said.

relay and occupying .a first position when. that relay is picked up but Shifting aftera slight delay to a second position when the code following relay releases, a source of feedback connects said feed backenergy source with said control circuit conductors and which in releas- ,50 energy, an impulserelay; which inpicking up ing interrupts that connection, an energizing.

circuit for said impulse relay whichcincludes -a back contact of said code following relay-corn; nected in series with a contact :ofsaid repeaterrelay that is closed'in said first'position and: over which each release of said code following relay contact momentarily picks up the impulse relay the off code period ofisaid release, means efe I and thereby causes said circuiticcnductors .to be supplied with a pulse :of .feed back energy during fective during eachof saidifo'ff' codeiperiods for preventing the said feed back energy that is then impressed upon the circuit conductors from picking up said code following relay, and 'traiiic governing apparatus controlled by thelpulses of said feed back energy which. said circuit conductors transmit.

11. In a railway signaling systern,i the combination of a control circuit icomprising'a pair of. conductors which normally are capable of trans;

mitting zenergybetweenagiven and opposite ends of the circuit-but which'at times are rendered incapable-of such transmission; means at-the given end of saidcircuit forsupplying said conductors with master code energy in the form of recurring on period .pulsesthat are separated by off period intervals, a code following relay at the opposite end of said circuit connected with said conductors and operated from a released to a picked up position by each of the said on period pulses of master code energy that said conductors transmit, a repeater relay controlled by said code-followingrelay and occupying a first position when-the code following relay is icked up but shifting after a slight delay to a second position upon each release of the code following relay, a source of feed back energy at said opposite circuit end, an impulse relay also at said opposite end which in picking up transfers the connection of said control circuit conductors from said code following relay to said feed back energy source and which in releasing restores the control circuit connection to the code following relay, an energizing circuit for said impulse relay which includes a back contact of said code following relay connected in series with a contact of said repeaterrelay that is closed in said first position and over which each release of said code following relay contact momentarily picks up the impulserelay and-thereby causes said control circuit conductors to be supplied with a pulse of feed back energy during the off code period of saidrelease, and traffic governing apparatus at said given circuit end controlled by the pulses of said feed back energy which are there received and selectively responsive according as said pulse reception does or does not continue.

12. In a railway signaling system, the combination of a section of track, means at the exit end of said section for supplying the section rails with master code energy in the form of recurring on period pulses that are separated by off period intervals, a code following track relay at the entrance end of said section connected with said rails and operated from a released to a picked up position by each of the said on period pulses of mastercodethat said rails transmit, a repeater relay controlled by said track relayand occupying a first position when the track'relay -is picked up but shifting after a slight delay to a second position upon each release of the track relay, a source of feed back energy at said section entrance end, an impulse relay also at said opposite end which in picking up transfers the connection of said rails from said track relay to said feed back energy source and whichin releasing restores the rail connection to the track relay, an energizing circuit for said impulse relay which includes a back contact of saidtrack relay connected in series with a contact-of said repeater relay thatis closed in said first position and over which each release of said track relay contact momentarily picks up the impulse relay and thereby causes said rails to besupplied with a pulse of feed back energy during the off code period of :said release, and traffic governingapparatus at said section exit controlled bythepulses of said feed back energy which are therereceived and selectively responsive according as said pulse reception does or does not continue..

FRANK Hi NICHOLSON. 

